This Week's Experiment - #251 Floating M's

This week's experiment is one that was mentioned on one of the museum
education e-mail lists. It started as a fun experiment and a wonderful
excuse to buy some chocolate candy. As I went along, I saw several marvelous
aspects to the science. To try this, you will need:

a bowl
some M&M candys
water

Put about an inch or two of warm water into the bowl. Select several candies
that have nice, clear "M"s on them. Place them, M side up, in the water.
Now watch carefully. Quickly, the candy coating starts to dissolve and the
colors settle to the bottom around the candy. The last part of the color to
go will probably be the part under the M. Slowly, a thin film with the M on
it will separate from the candy and float to the surface. If you let the
candy continue to dissolve, you will see a white candy layer under the
colored one and finally the chocolate center becomes visible.

I could not collect enough of the film that the M is printed on to be
certain, but it seems to be a very thin film of wax. It floats in water,
does not dissolve and leaves a waxy smear on a clean glass. Wax is also
edible, which is important with candy. You might try to think of other ways
to tell if it is wax or something else.

The M itself is made of titanium oxide, which is mined very near my home.
The sand in this part of Florida contains heavy, dark grains as well as the
white sand. These dark minerals contain titanium and they are mined by RGC
Minerals and used to make the titanium oxide that is used for the Ms on these
candies.

I found it very interesting that the dissolved colors stayed separate and
formed very sharp boundaries. I tried the experiment again with cold water
and found the color separation even more striking. Placing different colors
in a circle around the edge of the bowl formed triangular color segments that
looked like an artist's color wheel. The chemicals which produce the colors
have different densities. In past experiments we have separated these colors
by placing wet M&Ms on a coffee filter and watching the colors separate
through a process known as chromatography. I find it even more interesting
to see the colors forming such sharp boundaries in the water. I plan to do
some more investigation on this, so if you have any additional information
about it, I would love to see it.

There are all sorts of things you can try to take this farther. You might
try seeing how the temperature of the water changes the rate that the candy
dissolves. If you have a test tube or a very thin bud vase, try stacking
different colored candies and covering them with water to see if the colors
will form separate layers one on top of the other.

As you know, I always like to conserve and recycle the materials for the
experiments. When you finish, the candy is still perfectly edible, so don't
waste it. Just drain off the water and then scoop up the lumps of chocolate
for a snack.